单链表查找中间结点

单链表查找中间结点

题目描述：随机生成20个元素，构成一个链表，查找链表中间结点的值。
方法：快慢指针法
C++实现如下：

#include<iostream>
#include<ctime>
using namespace std;
#define SIZE 20
//链表中随机生成20个元素，查找中间结点的值
class ListNode
{
public:
	int Data;
	ListNode * Next;
};
ListNode* CreateList(int size) //生成链表
{
	ListNode* head = new ListNode;
	head->Next = NULL;
	for (int i = 0; i < size; i++)
	{
		ListNode* L = new ListNode;
		L->Data = rand() % 100 + 1; //1-100的随机数
		L->Next = head->Next;
		head->Next = L;
	}
	return head;
}
int main()
{
	srand((unsigned int)time(NULL));
	ListNode * L = CreateList(SIZE);
	
	//打印链表结点
	ListNode * p = L->Next;
	while (p != NULL)
	{
		cout << p->Data << " ";
		p = p->Next;
	}
	cout << endl;
	
	//查找中间结点的值
	//快慢指针法
	ListNode *fast, *low;
	fast = L; low = L;
	while (fast->Next != NULL)
	{
		//fast移动速度是low的2倍
		if (fast->Next->Next != NULL)
		{
			fast = fast->Next->Next;
			low = low->Next;
		}
		else
		{
			fast = fast->Next;
		}
	}
	cout << "中间结点的值为：" << low->Data << endl;

	system("pause");
	return 0;
}